Crystal controlled oscillator



DE WITT R. GODDARD 2 1 4 CRYSTAL CONTROLLED OSCILLATOR Original Filed June 4, 1931 mil INVENTOR DE wm R. GODDARD A'TTORNEY Patented May 19, 1936 2,041,408 CRYSTAL CONTROLLED OSCILLATOR De Witt R. Goddard, Riverhead,

N. Y., assignor to Radio Corporation of America, a corporation of Delaware Original application June 4, 1931, Serial No. this application July 8,

542,091. Divided and 1932, Serial No. 621,41

5 Claims. (Cl. 250-36) This case is directed towards Figure 6 of my copending application, Serial Number 542,091, filed June 4, 1931, and forms, of course, a divisional application thereof. In particular the present invention relates to an improved piezoelectric crystal controlled electron discharge device oscillator utilizing a pentode or five electrode tube.

It has been found that crystal controlled oscillators utilizing electron discharge devices of the triode type are very reluctant to oscillate with the crystal in circuit. Accordingly, the present invention has as its main object the provision of an oscillatory circuit utilizing piezo-electric crystal control which shall readily produce strong oscillations of constant frequency.

Broadly, according to the present invention, this object is performed by the provision of a five electrode tube together with appropriate circuits and a crystal for frequency controlling the oscillations produced by the tetrodes or pentodes used. The ready production of the oscillations according to my present invention, may be attributed to a large degree to the fact that the tubes used have a very high interelectrode impedance and consequently have much higher amplification which facilitates oscillation production.

Still a further object of my present invention is to provide an oscillator which shall be crystal controlled and in which the frequency of oscillation is very close to that of the natural crystal frequency. To do so, according to the present invention, use is made of impedances preferably in the form of resistances having no independent resonant characteristics of their own such as would provoke the generation of parasitic oscillations.

Other objects as well as advantages of the present invention will become apparent as the description thereof proceeds which description will be given with the aid of the accompanying drawing which is a wiring diagram of my improved crystal controlled oscillating circuit.

In the drawing, I have shown a crystal controlled oscillator comprising an electron discharge device wherein a crystal 2 is connected between the control electrode 60 and cathode 6 thereof. Output energy is taken from anode resistor I 3 connected to anode l2. Biasing potentials for the space charge grid 6| and screen grid 63 are taken respectively from potentiometers 65, 61, and anode potential is derived from potentiometer 69. The polarizing potential is fed, from an anode source (not shown), through conductor II.

This circuit will be found to oscillate strongly advantage that no oscillating circuits are present,

whichcircuits would tend to drag the crystal frequency, or cause the crystal to oscillate at a frequency rather far removed from its natural frequency.

Various modifications of the present invention will, of course, readily suggest themselves to those skilled in the art. Accordingly, the present invention is not to be limited by the exact circuits illustrated, but is to be given the full width and scope indicated by the appended claims.

Having thus described my invention, what I claim is:

1. Oscillation generating apparatus comprising an electron discharge device having an anode, a cathode, a grid adjacent said cathode, a grid adjacent said anode and a grid intermediate said grids, a non-reactive resistor connected between said anode and cathode, a two electrode piezoelectric crystal connected between said intermediate grid and said cathode, a resistance connected between said intermediate grid and cathode for establishing a suitable bias thereon, a circuit connected between the grid adjacent the cathode and the cathode for maintaining said grid adjacent the cathode highly positive with respect to said cathode, and, a polarizing circuit connected between the grid adjacent said anode and said cathode for maintaining said last mentioned grid at a suitable operating potential.

2. An oscillation generator comprising an electron discharge device having an anode, a cathode, a grid adjacent said anode, a grid adjacent said cathode, a grid intermediate said grids, a two electrode piezo-electric crystal connected between said intermediate grid and said cathode, biasing means connected between said intermediate grid and said cathode, means for suitably polarizing the grid adjacent said anode, a circuit for biasing the grid adjacent the cathode with respect to said cathode and a non-reactive resistance connected between said anode and cathode from which high frequency undulatory potentials may be derived.

3. An oscillation generator comprising an electron discharge device having an anode, a cathode, a grid, a screen grid and a space charge grid, means for maintaining said space charge grid at a slightly positive potential with respect to said cathode, a resistance connecting said grid to said cathode, a two electrode piezo-electric crystal connected in shunt to said resistance means for polarizing said screen grid to a positive potential 55 with respect to said cathode and, a non-reactive resistance connected between said anode and cathode, said last mentioned resistance being adapted to supply oscillatory output energy at a frequency closely corresponding to the natural frequency of said piezo-electric crystal.

4. An oscillation generator comprising an electron discharge device having an anode, a cathode and at least three other electrodes progressively,

spaced between the cathode and the anode, a source of potential the negative side of which is connected to said cathode, a purely resistive path extending from the positive side of said source to said anode, means including a non-reactive potentiometer arrangement connected across said source and having taps, one for so polarizing the electrode next the cathode that it is slightly more positive than the cathode, and another tap for so polarizing the electrode next the anode that it is suitably less positive than the anode, a nonreactive bias resistor interconnecting the oathode and the intermediate one of the progressively spaced electrodes, and a two-electrode piezo-electrio device in shunt with the last said resistor,

adapted to maintain constant the frequency of oscillations in said generator.

5. An oscillation generator comprising an electron discharge device having an anode, a cathode and at least three other electrodes progressively spaced between the cathode and the anode, a source of potential the negative side of which is connected to said cathode, a purely resistive path ,extending from the positive side of said source to said anode, means including non-reactive po tentiometers connected across said source and each having a tap, one tap for so polarizing the electrode next the cathode that it is slightly more positive than the cathode, and another tap for so polarizing the electrode next the anode that it is suitably less positive than the anode, a non-reactive bias resistor interconnecting the cathode and the intermediate one of the progressively spaced electrodes, and a two-electrode piezo-electric device in shunt with the last said resistor, adapted to maintain constant the frequency of oscillations in said generator.

DE WITT R. GODDARD. 

